EFFECT OF CITRUS RED MITE (ACARI, TETRANYCHIDAE) AND CULTURAL-PRACTICES ON TOTAL YIELD, FRUIT SIZE, AND CROP VALUE OF NAVEL ORANGE - YEAR-3AND YEAR-4

Direct and interacting effects of four seasons of uncontrolled citrus red mite, Panonychus citri (McGregor), populations with 36 other combi nations of grove management practices were examined to seek the existe nce of long-term deleterious consequences of not controlling mite popu lations on 'Navel' orange, Citrus sinensis (L.) Osbeck. Results from t he first 2 yr were published previously. In the 3rd and 4th yr, P. cit ri populations reached mean peak densities of 7.1 and 2.2 adult female P. citri per leaf at one site and 9.7 adult females per leaf at a sec ond site on trees where effective acaricides were withheld. These popu lations caused yield reductions of 9, 6.6, and 11.4%, respectively. Si multaneous increases in average fruit size of 2.3 and 2.1% were observ ed at the first site but not the second. Effects were confined to the season of differential acaricide application and did not carry over in to subsequent seasons. Total yield increased with increasing fertiliza tion level in the third and fourth year, as in the first 2 yr. Average fruit size decreased with increasing fertilization level in the third year but not the fourth. Fungicidenematicide treatments increased tot al yield and fruit size in both the 3rd and 4th yr. Growth regulator t reatments did not significantly affect total yield either year and cau sed a slight (1.0%) reduction in fruit size in the fourth year. Differ ential irrigation did not have a consistent, significant effect on tot al yield, but fruit size consistently increased significantly with inc reasing irrigation at both sites. Yield reductions from high P. citri populations were greater on nitrogen-stressed trees (16-18%) than on t rees that were fertilized conventionally (1-6%) or excessively (0-4%). Total yield and average fruit size did not differ consistently becaus e of any other interactions between effective P. citri treatments and other cultural practices. Marketing conditions continued to favor larg e fruit; thus, increases in average fruit size on trees where P. citri populations were not effectively suppressed continued to be at least a compensating, if not beneficial, consequence of withholding acaricid e applications.